The present invention relates to injection molding machines and, in particular, to an assembly for releasably supporting the extractor bars which interconnect a hydraulic ram to the extractor pin assembly of a molding machine die holder.
A reality of all injection molders is that of having to periodically change the sets of molding dies or cavities, which are mounted to the molding machine and which determine the configuration of the molded parts. While the complexity of the mold cavities can vary relative to the part being formed, they generally are secured to the molding machine via a relatively substantial outer housing or die holder which supports the dies in a fashion that permits a controlled separation and provides a coolant manifold to the channelways of the dies. Most commonly, one of the dies is slidably supported relative a rigidly mounted die which is secured to the die holder. The die holder, in turn, is secured to the molding machine. A plurality of extractor bars interconnect a hydraulic ram to an extractor pin assembly that mount adjacent the slide mounted die and whereby the movable die cavities can be separated from the rigid die, upon completion of a mold cycle, to permit extraction of the molded part.
Specifically, a pair of relatively long hexagonal or cylindrical shaped bars, variously referred to as ejector rods or extractor bars; extend between a plate mounted to one side of the movable die, which plate supports a plurality of smaller pins that pass through the movable die and push against the rigid die, and a ram plate at the end of the hydraulic piston. Each ejector bar is typically secured at its opposite ends via threaded mountings. That is, one end includes a threaded extension which mates with the plate member and the opposite end includes a coaxial, threaded bore which aligns with the ram plate. A screw fastener is insertable through the ram plate to draw each ejector bar to the ram plate.
In theory the foregoing mounting is not unduly cumbersome. In practice, however, and especially for a prototype or limited run production shop, numerous die changes may be required over the course of a day, with attendant compounding of lost production time. Because the ejector bars must be attached and re-attached with each die change, the tedious task of blindly aligning the ejector bars with the ram plate and screw fasteners can be rather costly.
In this regard, it is to be appreciated that a die change over is typically performed by the operator having to stand to one side or reach from the top into the center area of the molding machine, all without the advantage of being able to view the alignment of the bar bore relative to the ram plate. Oftentimes, therefore, the time to effect a die change depends on fortuity and one's luck in blindly aligning the piece parts. The time loss is compounded by the number of ejector bars which must be aligned.
The foregoing problems are indigenous to all injection molders of which applicant is aware and has been for numerous years. The only solution of which applicant is aware is a slotted nut assembly that may be manipulated to expose a longitudinal slot which permits the mounting of the nut assembly anywhere along the length of a threaded rod. Once mounted, the nut assembly is twisted to completely encircle the threaded rod and after which the nut may be tightened in conventional fashion.
In contrast to the foregoing, the present invention contemplates a clamping assembly which receives and self-aligns each ejector bar. Most important, the assembly is transversely accessible and operable relative to the ejector bars.